The mouse intestinal epithelium represents a continuous development system and provides a unique mammalian model for examining how cellular proliferation, lineage allocation (commitment), and differentiation are interrelated. The mechanisms that control cell lineage-specific, differentiation-dependent, region-appropriate and temporal patterns of gene expression in the perpetually renewing intestinal epithelium are largely unknown. This is due in large measure to the lack of an adequate, manipulatable assay system which retains the spatial and temporal complexities of the gut epithelium. We propose to continue our studies of the factors that modulate cellular differentiation programs along the crypt-to-villus and duodenal-to-colonic axes of the developing gut using normal, transgenic, and chimeric-transgenic mice. Four models are being employed. (1) Transgenic mice will be used to map cis-acting elements that regulate the distal-to-proximal wave of activation of the mouse ileal lipid binding protein gene (Ilbp) in the distal small intestine. This gene provides a model for initial patterning of the gut epithelium and is a sensitive marker of its stem cell hierarchy. (2) Transgenic and chimeric-transgenic mice will be used to evaluate the effects of E-cadherin, a dominant negative N-cadherin mutant, c-met and its ligand, scatter factor/hepatocyte growth factor, on the formation, organization, and functioning of the crypt-to-villus axis. (3) Transgenic mice that contain a cryptdin2-diphtheria toxin fusion gene will be used to assess the effects of the Paneth cell lineage on modulating proliferation and differentiation programs during and after formation of the crypt-to-villus axis. (4) Transgenic mice will be used to study the role of complex carbohydrates in regulating gastrointestina epithelial cell differentiation by both loss-of-function and gain-of- function experiments. This will be accomplished by expressing (i) influenza C virus 9-0-acetyl-5-N-acetyl-neuraminic acid-specific esterase, the Newcastle Disease virus N-acetyl-neuraminidase (sialidase) a human alpha1,2 specific fucosyltransferase, and a human alpha1,3/4 specific fucosyltransferase in undifferentiated, differentiating, and terminally differentiated members of gut epithelial cell lineages. Sinc the human H type1 and Lewisb blood group antigens mediate attachment of Helicobacter pylori to the human gut epithelium, the gain of function experiments should also allow us to create a transgenic mouse model for examining the effects of Helicobacter pylori on gut epithelial cell biology.